This invention relates to the field of stretch-wrap film packaging, in particular to a tool for dispensing highly stretchable plastic film for use in packaging.
The development of the stretch film wrap industry has brought about a need for devices capable of paying out film under variable tension as it is wrapped around a package or object or group of objects to be packaged together. Typically, such stretch-wrap film is supplied in rolls wound around a hollow core, and the film is unwound from the roll as it is applied. It is necessary as the film is unwound to apply a degree of tension to the unwinding end of the film so that the film will be somewhat stretched as it comes into contact with the object being packaged. For various reasons, it is desirable that the operator be easily able to control the degree of tension applied.
A number of such devices are already known. U.S. Pat. Nos. 4,179,081 and 4,248,392 issued Dec. 18, 1979 and February, 1981, respectively, to John C. Parry disclose devices with a flexible hand grip that is squeezed to exert a braking force to the core of a roll of film, whereby the operator may control the amount of tension on the film as it unrolls by varying the magnitude of pressure on the hand grip. These devices work particularly well with wider film rolls of 10 inches or greater with one such device at either end of the roll.
Tools for dispensing narrower stretch-wrap films, for example, those from one to five inches wide have also been made. With such narrower films, one-handed operation is often possible and more convenient. The Parry devices disclosed in the above-mentioned patents may be used for one-handed operation, but it has been found that the twisting torque resulting from one-handed operation may cause binding between the roll core and the hand grip, and a degree of loss of control of the tension.
U.S. Pat. No. 4,722,493 issued February, 1988 to Daniel J. Parry and John C. Parry discloses a device which uses the type of hand grip as discussed above and is well suited for one-handed operation. In this device, the roll core is engaged by a spindle which is freely rotatable with respect to a cylindrical handle. The flexible hand grip covers the handle and a collar attached to the spindle. With free rotation between the spindle and the handle, binding is avoided because the handle turns with the hand grip. Braking force is applied by the thumb and forefinger against the collar. It has been found, however, that in extended use with this type of arrangement the thumb and forefinger may become fatigued, resulting in a temporary impairment of ability to control the application of tension to the film.
U.S. Pat. No. 4,834,312 issued May 30, 1989 to Paul K. Riemenschneider discloses a dispenser wherein a head is affixed to a roll of film and a spindle extends from the head. A split cylinder forms a grip surrounding the spindle, and may be squeezed to exert frictional braking pressure. However, because the braking force is applied generally along the length of the spindle, this dispenser also tends to bind as a result of the twisting torque which results from one-handed operation.
Other more elaborate dispensers have also been made. It is desirable, however, that such devices be of simple, lightweight and inexpensive construction. In practice, such tools are easily lost or destroyed and through extensive use may require relatively frequent replacement. Lightness of weight is desirable to enable constant use without unnecessary expenditure of energy and resultant fatigue.